There may be many routes for a single address. For example, a webserver that is hosted in multiple datacenters may yield multiple IP addresses in its DNS response.

In limited situations OkHttp will retry a route if connecting fails:

problems. If your service has multiple IP addresses, OkHttp will attempt alternate addresses if the
first connect fails. This is necessary for IPv4+IPv6 and services hosted in redundant data
centers. OkHttp supports modern TLS features (TLS 1.3, ALPN, certificate pinning). It can be
configured to fall back for broad connectivity.

}

func hostResolveToLocalhost(endpoint Endpoint) bool {
	hostIPs, err := getHostIP(endpoint.Hostname())
	if err != nil {
		return false
	}
	var loopback int
	for _, hostIP := range hostIPs.ToSlice() {
		if net.ParseIP(hostIP).IsLoopback() {
			loopback++
		}
	}
	return loopback == len(hostIPs)
}

// UpdateIsLocal - resolves the host and discovers the local host.

		Code:       err.Code,
		Message:    errBody,
		Resource:   reqURL.Path,
		BucketName: reqInfo.BucketName,
		Key:        reqInfo.ObjectName,
		RequestID:  w.Header().Get(xhttp.AmzRequestID),
		HostID:     globalDeploymentID(),
	}
	encodedErrorResponse := encodeResponseJSON(errorResponse)
	writeResponse(w, err.HTTPStatusCode, encodedErrorResponse, mimeJSON)

If the client tries to go to `/items`, by default, it would be redirected to `/items/`.

But before setting the *CLI Option* `--forwarded-allow-ips` it could redirect to `http://localhost:8000/items/`.

But maybe your application is hosted at `https://mysuperapp.com`, and the redirection should be to `https://mysuperapp.com/items/`.

By setting `--proxy-headers` now FastAPI would be able to redirect to the right location. 😎

```
https://mysuperapp.com/items/

   *
   * @since 15.0
   */
  public static final MediaType KEY_ARCHIVE = createConstant(APPLICATION_TYPE, "pkcs12");

  /**
   * This is a non-standard media type, but is commonly used in serving hosted binary files as it is
   * <a href="http://code.google.com/p/browsersec/wiki/Part2#Survey_of_content_sniffing_behaviors">
   * known not to trigger content sniffing in current browsers</a>. It <i>should not</i> be used in

				Code:       serr.ErrorCode(),
				Message:    serr.ErrorMessage(),
				BucketName: bucket,
				Key:        object,
				Resource:   r.URL.Path,
				RequestID:  w.Header().Get(xhttp.AmzRequestID),
				HostID:     globalDeploymentID(),
			})
			writeResponse(w, serr.HTTPStatusCode(), encodedErrorResponse, mimeXML)
		} else {
			writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		}
		return
	}

    val hostNfc = "café.com"
    val hostNfcPunycode = "xn--caf-dma.com"
    val hostNfd = "café.com"
    val hostNfdPunycode = "xn--cafe-yvc.com"
    assertEquals(hostNfcPunycode, "http://$hostNfc/".toHttpUrl().host)
    assertEquals(hostNfcPunycode, "http://$hostNfcPunycode/".toHttpUrl().host)
    assertEquals(hostNfcPunycode, "http://$hostNfd/".toHttpUrl().host)

						errorRespJSON = encodeResponseJSON(APIErrorResponse{
							Code:      hr.apiErr.Code,
							Message:   hr.errBody,
							Resource:  r.URL.Path,
							RequestID: w.Header().Get(xhttp.AmzRequestID),
							HostID:    globalDeploymentID(),
						})
					}
					if !started {
						setCommonHeaders(w)
						w.Header().Set(xhttp.ContentType, string(mimeJSON))
						w.WriteHeader(hr.apiErr.HTTPStatusCode)
					}

*.eu-west-2.airflow.amazonaws.com
*.eu-west-3.airflow.amazonaws.com
*.ewp.live
*.ex.futurecms.at
*.ex.ortsinfo.at
*.experiments.sagemaker.aws
*.firenet.ch
*.fk
*.frusky.de
*.futurecms.at
*.gateway.dev
*.hosted.app
*.hosting.myjino.ru
*.hosting.ovh.net
*.id.pub
*.il-central-1.airflow.amazonaws.com
*.in.futurecms.at
*.jm
*.kawasaki.jp
*.kh
*.kin.one
*.kin.pub
*.kitakyushu.jp
*.kobe.jp